What Snakes Found In New England Fresh Water Are Poisonous?

None. Zero, Zilch.  There are NO "poisonous" snakes anywhere on the entire planet!  A poison is a toxic substance that must be swallowed or inhaled in order to cause harm; chlorine bleach and anti-freeze are two good examples.  You can eat any snake without any ill effects, unless you choke on a bone.  New England has only two VENOMOUS snakes, the Timber Rattlesnake(Crotalus horridus) and the Northern Copperhead(Agkistrodon contortrix mokassen).  While both can swim, they aren't usually found in water, per se.  A snake that IS often found in fresh water, and IS native to New England, is the large Northern Water Snake(Nerodia sipedon), which is a harmless, non-venomous species that is often incorrectly identified as a "Water Moccasin".  There are no Water Moccasins any further north than southern Virginia.